json数据的转义

{
"DSGA": {
"approval": "qatest_nj"
},
"applydetailId": "29895",
"approveResult": "1",
"channelCode": "crm",
"channelMembercode": "10013538576",
"productCode": "DSGA"
}

         StringBuffer st=new StringBuffer();
         st.append("{");
         st.append("\"approveResult\"").append(":").append("\"1\"").append(",");
         st.append("\"channelCode\"").append(":").append("\"crm\"").append(",");
         st.append("\"DSGA\"").append(":").append("{").append("\"approval\"").append(":").append("\"qatest_nj\"").append("}").append(",");
         st.append("\"productCode\"").append(":").append("\"DSGA\"").append(",");
         st.append("\"applydetailId\"").append(":").append("\"29895\"").append(",");
         st.append("\"channelMembercode\"").append(":").append("\"10013538576\"").append(",");
         st.append("\"approveAdvice\"").append(":").append("null");
         st.append("}");
         String string = st.toString();