diff --git a/testable-agent/pom.xml b/testable-agent/pom.xml
index 09d9e85..5b5ffdd 100755
--- a/testable-agent/pom.xml
+++ b/testable-agent/pom.xml
@@ -10,7 +10,11 @@
   <name>testable-agent</name>
 
   <properties>
+    <java.version>1.6</java.version>
+    <project.compiler.level>1.6</project.compiler.level>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <asm.lib.version>8.0.1</asm.lib.version>
+    <plugin.compiler.version>3.8.1</plugin.compiler.version>
     <plugin.jar.version>3.2.0</plugin.jar.version>
     <plugin.shade.version>3.2.4</plugin.shade.version>
   </properties>
@@ -32,6 +36,16 @@
   <build>
     <finalName>testable-agent</finalName>
     <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-compiler-plugin</artifactId>
+        <version>${plugin.compiler.version}</version>
+        <configuration>
+          <source>${project.compiler.level}</source>
+          <target>${project.compiler.level}</target>
+          <encoding>${project.build.sourceEncoding}</encoding>
+        </configuration>
+      </plugin>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-jar-plugin</artifactId>
diff --git a/testable-core/pom.xml b/testable-core/pom.xml
index cc4faa0..8bacc5d 100644
--- a/testable-core/pom.xml
+++ b/testable-core/pom.xml
@@ -11,10 +11,10 @@
     <name>testable-core</name>
 
     <properties>
-        <plugin.compiler.version>3.8.1</plugin.compiler.version>
-        <plugin.resources.version>3.1.0</plugin.resources.version>
+        <java.version>1.6</java.version>
+        <project.compiler.level>1.6</project.compiler.level>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <project.compiler.level>1.7</project.compiler.level>
+        <plugin.compiler.version>3.8.1</plugin.compiler.version>
     </properties>
 
     <dependencies>
diff --git a/testable-core/src/main/java/com/alibaba/testable/core/translator/EnableTestableTranslator.java b/testable-core/src/main/java/com/alibaba/testable/core/translator/EnableTestableTranslator.java
index 11c56f3..7473891 100644
--- a/testable-core/src/main/java/com/alibaba/testable/core/translator/EnableTestableTranslator.java
+++ b/testable-core/src/main/java/com/alibaba/testable/core/translator/EnableTestableTranslator.java
@@ -19,9 +19,9 @@ import java.lang.reflect.Modifier;
 public class EnableTestableTranslator extends BaseTranslator {
 
     private final String sourceClassName;
-    private final ListBuffer<Name> sourceClassIns = new ListBuffer<>();
-    private final ListBuffer<String> privateOrFinalFields = new ListBuffer<>();
-    private final ListBuffer<String> privateMethods = new ListBuffer<>();
+    private final ListBuffer<Name> sourceClassIns = new ListBuffer<Name>();
+    private final ListBuffer<String> privateOrFinalFields = new ListBuffer<String>();
+    private final ListBuffer<String> privateMethods = new ListBuffer<String>();
     private final PrivateAccessStatementGenerator privateAccessStatementGenerator;
 
     public EnableTestableTranslator(String pkgName, String testClassName, TestableContext cx) {
diff --git a/testable-core/src/test/java/com/alibaba/testable/core/util/StringUtilTest.java b/testable-core/src/test/java/com/alibaba/testable/core/util/StringUtilTest.java
index b81a446..131a3a1 100644
--- a/testable-core/src/test/java/com/alibaba/testable/core/util/StringUtilTest.java
+++ b/testable-core/src/test/java/com/alibaba/testable/core/util/StringUtilTest.java
@@ -11,7 +11,7 @@ class StringUtilTest {
 
     @Test
     void should_able_to_join_string() {
-        List<String> list = new ArrayList<>(4);
+        List<String> list = new ArrayList<String>(4);
         list.add("a");
         list.add("b");
         list.add("c");
diff --git a/testable-maven-plugin/pom.xml b/testable-maven-plugin/pom.xml
index 619997f..5b4cc57 100644
--- a/testable-maven-plugin/pom.xml
+++ b/testable-maven-plugin/pom.xml
@@ -9,8 +9,12 @@
   <url>http://maven.apache.org</url>
 
   <properties>
-    <java.version>1.8</java.version>
     <testable.version>0.2.0-SNAPSHOT</testable.version>
+    <java.version>1.6</java.version>
+    <project.compiler.level>1.6</project.compiler.level>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    <plugin.compiler.version>3.8.1</plugin.compiler.version>
+    <maven.plugin.version>3.6.0</maven.plugin.version>
   </properties>
 
   <dependencies>
@@ -39,10 +43,20 @@
 
   <build>
     <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-compiler-plugin</artifactId>
+        <version>${plugin.compiler.version}</version>
+        <configuration>
+          <source>${project.compiler.level}</source>
+          <target>${project.compiler.level}</target>
+          <encoding>${project.build.sourceEncoding}</encoding>
+        </configuration>
+      </plugin>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-plugin-plugin</artifactId>
-        <version>3.6.0</version>
+        <version>${maven.plugin.version}</version>
       </plugin>
     </plugins>
   </build>