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Merge pull request #16 from antkorwin/support-for-interfaces
Support for interfaces
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‎README.adoc

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# Better Strings - Java String Interpolation
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image:https://travis-ci.com/antkorwin/better-strings.svg?branch=master["Build Status", link="https://travis-ci.com/antkorwin/better-strings"]
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image:https://travis-ci.com/antkorwin/better-strings.svg?branch=master["Build Status",link="https://travis-ci.com/antkorwin/better-strings"]
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image:https://codecov.io/gh/antkorwin/better-strings/branch/master/graph/badge.svg[link ="https://codecov.io/gh/antkorwin/better-strings"]
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image:https://maven-badges.herokuapp.com/maven-central/com.antkorwin/better-strings/badge.svg[link="https://search.maven.org/search?q=g:com.antkorwin%20AND%20a:better-strings"]
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The Java Plugin to use string interpolation for Java (like in Kotlin).
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Supports Java 8, 9, 10, 11, ...
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## Motivation
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In the latest JEPs https://openjdk.java.net/jeps/355, we have the only expectation of the RAW string literals,
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but there is nothing about the string interpolation.
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In the latest JEPs https://openjdk.java.net/jeps/355, we have the only expectation of the RAW string literals, but there is nothing about the string interpolation.
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And it’s so sad, that we need writing code like this in the 2020 year:
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[source, java]
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[source,java]
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----
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int a = 3;
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int b = 4;
@@ -29,7 +27,7 @@ just to print the string: `3 + 4 = 7`
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of course, we can use a `var` since Java 10:
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[source, java]
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[source,java]
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----
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var a = 3;
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var b = 4;
@@ -42,7 +40,7 @@ But this code is still sad =(
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### Using variables in string literals
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[source, java]
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[source,java]
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----
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var a = 3;
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var b = 4;
@@ -53,24 +51,26 @@ prints: `3 + 4 = 7`
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### Using expressions
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[source, java]
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[source,java]
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----
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var a = 3;
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var b = 4;
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System.out.println("flag = ${a > b ? true : false}");
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----
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prints: `flag = false`
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[source, java]
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[source,java]
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----
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var a = 3;
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System.out.println("pow = ${a * a}");
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----
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prints: `pow = 9`
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### Using functions
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[source, java]
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[source,java]
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----
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@Test
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void functionCall() {
@@ -85,21 +85,83 @@ long factorial(int n) {
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return fact;
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}
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----
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prints: `fact(5) = 120`
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### Using string interpolation in class fields
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you can use better-string for string interpolation in class fields, for example:
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[source,java]
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----
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public class Test {
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public String field = "${3+4}";
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public String getField(){
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return "field = ${field}";
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}
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}
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----
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`new Test().getField()` prints : `field = 7`
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### Using string interpolation in default methods of interfaces
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also you can use string interpolation with default methods in interfaces like this:
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[source,java]
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----
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public interface InterfaceWithDefaultMethod {
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default String sum(){
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return "sum = ${1+2}";
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}
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}
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public class Test implements InterfaceWithDefaultMethod {
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public String test() {
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return sum();
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}
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}
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----
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The result of `new Test().test()` is `sum = 3`
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### Using string interpolation in enums
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In addition you can use string interpolation for code of enums:
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[source, java]
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----
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public enum EnumCode {
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FIRST,
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SECOND,
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THIRD;
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@Override
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public String toString() {
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return "value: ${this.name()}, order: ${this.ordinal() + 1}";
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}
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}
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----
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`EnumCode.THIRD.toString();` should print: `value: THIRD, order: 3`
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### Limitations
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It's impossible to use the string interpolation within annotations value.
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It provides compatibility with spring framework properties injecting by the `@Value` annotation.
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### Disclaimer
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NOTE: Keep in mind that this feature should be used carefully.
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You shouldn't write too much code inside string literals
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because it is too difficult to maintain and maybe not obvious for debugging.
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You shouldn't write too much code inside string literals because it is too difficult to maintain and maybe not obvious for debugging.
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## Getting started
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You need to add the following dependency:
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[source, xml]
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[source,xml]
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----
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<dependency>
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<groupId>com.antkorwin</groupId>
@@ -114,7 +176,7 @@ And you can use string interpolation anywhere in your code.
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To skip the string interpolation for class, method or field you can use the `@DisabledStringInterpolation` annotation:
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[source, java]
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[source,java]
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----
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@DisabledStringInterpolation
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class Foo {
@@ -126,66 +188,58 @@ class Foo {
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this code prints: `${a+b}`
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Also, you can use the following workaround
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to escape string interpolation locally in your code:
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Also, you can use the following workaround to escape string interpolation locally in your code:
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[source, java]
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[source,java]
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----
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System.out.println("${'$'}{a+b}");
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----
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the result is : `${a+b}`
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## How to control the generated code
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Better Strings is a Java Annotation Processor,
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but it does not process specific annotations, it makes AST modification of your code while javac compiling it.
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Better Strings is a Java Annotation Processor, but it does not process specific annotations, it makes AST modification of your code while javac compiling it.
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By default, each `${...}` occurrence translates into an invocation of `String#valueOf`.
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For instance, a string:
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[source, java]
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[source,java]
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----
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"Result: ${obj}.method() = ${obj.method()}"
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----
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will yield:
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[source, java]
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[source,java]
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----
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"Result: "
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+ String.valueOf(obj)
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+ ".method() = "
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+ String.valueOf(obj.method())
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----
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Under certain circumstances (e.g. with certain static code analyzers), however,
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it might be preferred that the generated code contains an explicit `toString` invocation for each `${...}` occurrence containing a non-null value.
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Under certain circumstances (e.g. with certain static code analyzers), however, it might be preferred that the generated code contains an explicit `toString` invocation for each `${...}` occurrence containing a non-null value.
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This can be controlled with `-AcallToStringExplicitlyInInterpolations` compiler option, which will instead make the above string translate into:
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[source, java]
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[source,java]
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----
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"Result: "
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+ (java.util.Objects.nonNull(obj) ? java.util.Objects.requireNonNull(obj).toString() : "null")
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+ ".method() = "
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+ (java.util.Objects.nonNull(obj.method()) ? java.util.Objects.requireNonNull(obj.method()).toString() : "null")
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----
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NOTE: this causes the inner part of each `${...}` to be evaluated twice,
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which might be problematic if the expression is side-effecting, non-deterministic or expensive to compute.
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NOTE: this causes the inner part of each `${...}` to be evaluated twice, which might be problematic if the expression is side-effecting, non-deterministic or expensive to compute.
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## How to use with other annotation processors
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If you need to use multiple annotation processors (for example `better-strings` with `lombok` or `mapstruct`)
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and the order of processing is necessary for you then you can set the order in your building tool.
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If you need to use multiple annotation processors (for example `better-strings` with `lombok` or `mapstruct`) and the order of processing is necessary for you then you can set the order in your building tool.
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In maven, you should declare dependencies as usually,
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then describe annotation processors in the configuration of the `maven-compiler-plugin`
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In maven, you should declare dependencies as usually, then describe annotation processors in the configuration of the `maven-compiler-plugin`
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in the build section:
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[source, xml]
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[source,xml]
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----
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>

‎pom.xml

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<groupId>com.antkorwin</groupId>
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<artifactId>better-strings</artifactId>
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<packaging>jar</packaging>
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<version>0.4</version>
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<version>0.5-SNAPSHOT</version>
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<!-- region Info -->
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<name>BetterStrings Java Plugin</name>

‎src/main/java/com/antkorwin/betterstrings/BetterStringsProcessor.java

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private boolean isClassOrEnum(Element codeElement) {
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return codeElement.getKind() == ElementKind.CLASS ||
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codeElement.getKind() == ElementKind.INTERFACE ||
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codeElement.getKind() == ElementKind.ENUM;
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}
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‎src/test/java/com/antkorwin/betterstrings/BetterStringsProcessorTest.java

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assertThat(result).isEqualTo("password = 1234");
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}
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@Test
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void interpolationInFields() {
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@Language("Java") String classCode = "public class Test { " +
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" public String field = \"${3+4}\";" +
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" public String getField(){ " +
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" return \"${field}\";" +
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" }" +
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"}";
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Object result = instantiatedTestClass(classCode).invoke("getField");
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assertThat(result).isEqualTo("7");
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}
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@Nested
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class DisabledAnnotationTests {
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assertThat(result).isEqualTo("SECOND = 7");
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}
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@Test
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void enumToString() {
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@Language("Java") String enumCode = "public enum EnumCode {" +
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" FIRST," +
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" SECOND," +
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" THIRD;" +
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" @Override" +
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" public String toString() {" +
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" return \"value: ${this.name()}, order: ${this.ordinal() + 1}\";" +
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" }"+
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"}";
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@Language("Java") String classCode = "public class Test { " +
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" public static String test(){ " +
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" return EnumCode.THIRD.toString();" +
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" }" +
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"}";
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Object result = new CompileTest().classCode("Test", classCode)
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.classCode("EnumCode", enumCode)
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.processor(new BetterStringsProcessor())
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.compile()
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.loadClass("Test")
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.invokeStatic("test");
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assertThat(result).isEqualTo("value: THIRD, order: 3");
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}
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}
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@Nested
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class Interfaces {
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@Test
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void useInDefaultMethod() {
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@Language("Java") String interfaceCode = "public interface InterfaceWithDefault {" +
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" default String sum(){" +
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" return \"${1+2}\";" +
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" }" +
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"}";
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@Language("Java") String classCode = "public class Test implements InterfaceWithDefault {" +
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" public String test() {" +
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" return sum();" +
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" }" +
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"}";
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Object result = new CompileTest().classCode("Test", classCode)
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.classCode("InterfaceWithDefault", interfaceCode)
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.processor(new BetterStringsProcessor())
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.compile()
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.createClass("Test")
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.invoke("test");
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assertThat(result).isEqualTo("3");
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}
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@Test
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void useInFields() {
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@Language("Java") String interfaceCode = "public interface InterfaceWithDefault {" +
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" int a = 2;" +
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" String b = \"${a*2}\";" +
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" default String mul(){" +
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" return b;" +
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" }" +
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"}";
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@Language("Java") String classCode = "public class Test implements InterfaceWithDefault {" +
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" public String test() {" +
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" return mul();" +
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" }" +
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"}";
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Object result = new CompileTest().classCode("Test", classCode)
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.classCode("InterfaceWithDefault", interfaceCode)
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.processor(new BetterStringsProcessor())
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.compile()
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.createClass("Test")
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.invoke("test");
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assertThat(result).isEqualTo("4");
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}
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}
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@Nested

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